Ok, physics 101: shooting someone in a car is stupid movie crap.
If a car is going to hit you in a few seconds, even if you draw, fire, and blow the driver's head to bits, the sheer momentum will still make you roadkill. A car with a dead driver will just keep moving however fast it was going. Sure, it'll slow or veer *eventually*, but if you're far enough away for either of those possibilities, you didn't need to shoot.
I'm not saying the cops were wrong or right, I'm saying they've watched *WAY* too many action movies. I'd like to hear any incidence where shooting the driver of a moving vehicle seconds away from splattering you has done a damned bit of good, rather than simply demonstrating a fatal lack of understanding of basic physics.